1. Field of the Invention
The present invention relates to a band converter and a related satellite television system, and more particularly, to a band converter and a related satellite television system capable of improving signal quality and manufacturing yield rate.
2. Description of the Prior Art
Satellite communication system has characteristics of broadband transmission and wide coverage, so it is widely applied to detection systems, military, telecommunication networks, data, mobile communications, and other fields.
As far as ground users of the satellite communication system are concerned, an antenna, a low-noise block down-converter (LNB), and a demodulator are required to be able to receive a satellite signal. The satellite signal is first received by the antenna, then down-converted into an intermediate frequency (IF) signal via the LNB, and finally demodulated to generate a play signal by the demodulator to be outputted to a user device (e.g., a television).
Please refer to FIG. 1 together with FIG. 2. FIG. 1 is a spectrum diagram of a down-converted satellite signal 100, and FIG. 2 is a diagram illustrating the down-converted satellite signal 100 shown in FIG. 1 processed by a band converter 200. As shown in FIG. 1, the down-converted satellite signal 100 consists of a first data signal DS1 located at a first frequency band FB1, a second data signal DS2 located at a second frequency band FB2, a third data signal DS3 located at a third frequency band FB3, wherein the third frequency band FB3 is higher than the second frequency band FB2, and the second frequency band FB2 is higher than the first frequency band FB1.
A current receiver (e.g. a narrow band receiver 240) is capable of receiving the data signals located at the second frequency band FB2 and the third frequency band FB3 only, and is unable to receive the first data signal DS1 located at the first frequency band FB1. For this reason, a band converter 200 is required to be added in front of the narrow band receiver 240 in order to have an option to receive all of the data signals by stages. As shown in FIG. 2, the band converter 200 can select to output a first output signal 210 or a second output signal 220 to the narrow band receiver 240 through the control of a selecting signal SEL1, wherein the first output signal 210 consists of the second data signal DS2 located at the second frequency band FB2 as well as the third data signal DS3 located at the third frequency band FB3, and the second output signal 220 consists of the second data signal DS2 located at the second frequency band FB2 as well as the up-converted first data signal DS1 located at the third frequency band FB3.
Please refer to FIG. 3. FIG. 3 is a diagram showing an architecture of a traditional B-band converter 300. AS shown in FIG. 3, the B-band converter 300 includes a first power distributor 310, a first high-pass filter HPF1, a second power distributor 320, a band-pass filter BPF1, a low-pass filter LFP1, a mixer 330, a local oscillator 340, a second high-pass filter HPF2, a third power distributor 350, a switch circuit 360, a micro-controller 370, and a second low-pass filter LPF2. From FIG. 3, we can see that the down-converted satellite signal 100 shown in FIG. 1 is received by the B-band converter 300 and is processed by its internal components, wherein the switch circuit 360 is used for selecting to output the first output signal 210 or the second output signal 220 to the back-end narrow band receiver (not shown).
The B-band converter 300 shown in FIG. 3 is an available product in the current market, but its circuit structure is complicated to be implemented. Hence, how to improve signal quality, simplify circuits, and save cost have become an important topic of this field.